1. Field of the Invention
This invention relates to hose constructions and more particularly to a hose for use in transporting or otherwise handling refrigerants predominantly of 1,1,1,2-tetrafluoroethane.
2. Description of the Prior Art
Dichlorodifluoromethane among various gases of Freon TM, commonly called CFC 12, has been reputed as a refrigerant fluid for instance in car coolers used under adversely vibrating conditions. To suit the transport of CFC 12 a variety of hoses are known, a typical example of which is built with an inner tube formed of a rubber of high resistance to gas leak, say a nitrile-butadiene rubber (NBR) for CFC 12. Another hose involves the assembly of an inner tube of a composite structure having a resinous layer and a rubbery layer.
From protective standpoints of global environment, however, the current trends in industry have been directed toward phasing out the use of CFC 12 tending to cause ozone depletion. CFC 12 is extremely undecomposable and necessarily afloat in the troposphere over a long period of time. The gas in turn rises into the stratophere where it decomposes on exposure to ultraviolet rays and develops chlorine with the results that the byproduct invites catalytic destruction of ozone, eroding the ozone layer that screens out dangerous solar rays. This will in some instances induce physical hazards such as cutaneous cancer, catarast and deficient immunity.
Included in good replacements is 1,1,1,2-tetrafluoroethane, CF.sub.3 CH.sub.2 F, also termed HFC 134a. Due to the hydrogen atoms present in the molecule, such chemical is relatively easy to decompose even in the troposphere. This means that HFC 134a will provide less tendency of entering the stratophere, and even if so, damaging the ozone layer as it has no chlorine atoms in the molecule.
The HFC 134a gas has been found considerably different from CFC 12 in regard to the physicochemical behavior against rubber material; that is, NBR rubbers in actual use are not effective to attain impermeability of HFC 134a as against CFC 12. An urgent need, therefore, has arisen for hoses that can exhibit sufficient leak resistance to HFC 134a and other important qualities including water proofness and heat resistance.